Touring - efficiency, gear inches, wheel size

One arguement I've heard for a larger wheel is greater efficiency. Is that true?

If you compare two different wheel sizes -- using the same rings, cogs, cranks -- then the smaller wheel has less gear inches. Would it be correct to say that the smaller wheel is easier to turn then?

If that's the case, you could simply put the smaller wheeled bike into one cog harder to achieve the same ground speed as the bigger wheel using the SAME amount of energy, correct? (I know I'm generalizing)

The point of my question is... for the purpose of getting from Point A to Point B using he same amount of energy, bikes with two different size wheels would get there at the same time, correct?

If true, then for the point of efficiency, there really is no difference between a 26" wheel and a 29" wheel with respect to diameter?


(If this is true, then I wonder where I got the impression that 700c wheels are "better" than 26" wheels? Is this a common misconception?)

I think a number of your premises are incorrect. For instance if I have two wheels on my bike, one made of lead and the other of the usual stuff, but both "get there at the same time", that doesn't mean they are equally efficient. etc...

That said, 700c wheels are not necessarily more efficient than 26" wheels, in fact the reverse may be true on the touring bike.

The main argument between the types seems to be that 26" wheels are better for their lighter weight, assuming identical components. 700c wheels are better because they roll more smoothly over bumps. The former is good for acceleration (which is an ongoing issue, just stop pedaling and see where that gets you), the latter for maintaining your speed. Of the two, the first is more reliable, you can't be sure that you will gain the claimed advantage with rolling resistance. On a perfectly flat surface the issue wouldn't present while the lighter weight is still an advantage. On rough surfaces it's complicated, there are some situations where one or the other wheel would be better. In general the larger wheel may not roll more efficiently always, but it probably feels better to the human on the seat.

Beyond such arguments there are practical considerations. If the wheels get too small higher speeds get harder to achieve with standard components and mechanical drag may start to be issues. So racing bikes need the bigger wheels to be fast, for gearing reasons, possibly, not just because of efficiency.

There are other issues, like braking, where wheel size is an issue.

Overall I think 26" wheels have the edge, but I don't really know since to date I have not been able to compare identical bikes that differed only in the size of the wheels.

I'm sorta working on a 69er at the moment (26" and 700c on one bike). Easy to think about, not sure I will have the guts when the torch gets lit. Hard to put a lot of effort into something most people will probably hate. The 69er argument goes two ways, either you figure it's a magic bullet combination, or you figure it just works in a particular situation. Mine is more in the latter camp since I feel the Rohloff I am making only belongs on a 26" wheel since it's 32 hole, and I like a big wheel up front because it is more comfortable. But I do expect it to have a little magic as well. I am looking forward to more cargo space in the rear also. Stupidest thing is the supply issue for wheel parts. I guess if you look at it as a 700c bike that I reduced the size of the rear wheel of, and am now forced to carry an extra fold-up and innertubes for, then you probably still come out ahead since at least the extra load isn't located in the rear wheel circumference.

While I don't think the 69er in MTB land translates to touring much, it does explain some principles, and starts one thinking with split vision.


http://www.trekbikes.com/us/en/bikes/2008/mountain_hardtail/69er/69ersinglespeed/

http://www.cyclingnews.com/tech.php?id=tech/2005/news/08-29

I think the biggest factor between the two different rim sizes would be tire availability.I don't think you can get as thin a tire for the 26" size than the 29"or700C.Rolling resistance from the tires would be the biggest difference IMHO.

That is a point though there are very narrow tires in some lessor known brands for the 26, and the whole 29er thing for 700c, even though rims and clearances will probably govern your results.

The way I look at it is that either is super fine for touring. you can easily get 32 and fatter wheels for 26", and you can easily get 38 and narrower tires for the 700c. So if your side use for the bike is road racing, or credit card touring, then maybe go for the 700c for various reasons. If your side use includes mud the 26" has the tires for you. Realistically the 26" probably covers more useful sizes if we are talking loaded touring because that includes roads right through to offroads, and the 26 has all the sizes.

y'all are missing the question...

EVERYTHING being EQUAL*... is there a speed difference between the two wheels?


* as for gearing, let say that can be different so we're comparing equal wattage output.

No, that is the exact question I dealt with in the first response. Identical hubs, rims, spokes, and tires, which I have on the premises. When that is in place you can start to discuss the differences in terms of acceleration and rolling. Even if you can decide on those points in the real world you still have to deal with the rest of it.

There are some makers out there that do a fair number of tourers in 26, and 700C, on the same size frames. And for what it is worth, you don't really hear them prescribing either one for speed, from which I conclude the difference isn't dramatic, or even discernable.

Speed is a pretty tough concept since it can mean a lot of things. Are we talking high speeds, low speeds maintanined longer (touring case mostly), speeds over given surfaces, into the wind, uphill, etc...

You may be able to accelerate quicker with the small wheel due to less rotating mass, but the larger diameter wheel can keep its inertia longer so you may be expending less energy to keep a sustained speed.

One arguement I've heard for a larger wheel is greater efficiency. Is that true?
Not really. Not sure where you picked that one up from by the way, since the argument is normally that smaller wheels are faster. ;) This spurred some tri athletes to use 650c wheels instead of 700c for awhile.



If you compare two different wheel sizes -- using the same rings, cogs, cranks -- then the smaller wheel has less gear inches. Would it be correct to say that the smaller wheel is easier to turn then?
Different sized wheels will require different gearing. E.g. 26T (front) x 25T (back) on 700c is about the same as 42T x 32T with 20" wheels.

However, if you are at 25 gear inches, you are at 25 gear inches, no matter what size wheels. You will still need to put out pretty much the same wattage to cover the exact same terrain.



The point of my question is... for the purpose of getting from Point A to Point B using he same amount of energy, bikes with two different size wheels would get there at the same time, correct? If true, then for the point of efficiency, there really is no difference between a 26" wheel and a 29" wheel with respect to diameter?
Correct

The differences, as others pointed out, are tire availability; comfort; and a small aero advantage. Smaller wheels will also accelerate a little faster and will steer faster; so compared to 700c, a 20" wheeled bike will have lots of oversteer, and 29" wheels will feel more stable (and steer a little more sluggishly). 700c is very easy to get in the US and Europe, but iirc 26" is easy elsewhere (particularly Central / South America).

[QUOTE=Peterpan1;5447458]
I'm sorta working on a 69er at the moment (26" and 700c on one bike). Easy to think about, not sure I will have the guts when the torch gets lit. Hard to put a lot of effort into something most people will probably hate. The 69er argument goes two ways, either you figure it's a magic bullet combination, or you figure it just works in a particular situation.

While I don't think the 69er in MTB land translates to touring much, it does explain some principles, and starts one thinking with split vision.
[\qoute]

Hey I am also working on my 69 but I am going to use the bike for offroad (mainly) tourism. I am going to use special designed by titerra (titerra.com) ti front fork (29'') and ti frame (26''). I do not believe 69 is better for cross country race but for offroad cycling especially with rigid fork is a really good idea.

You may be able to accelerate quicker with the small wheel due to less rotating mass, but the larger diameter wheel can keep its inertia longer so you may be expending less energy to keep a sustained speed.

No a large wheel has more inetria because of the weight being further way from the center so more energy was put into start with hence will have more to get rid of when slowing down. Wheels of diffrent sizes do not store enegy more efficently than one another bigger wheels just store more so more was put in the first place.

Infact using a idalized situation as far a s bearing are concerned a small wheel is more efficent. Due to the fact that more energy is put into the large wheel to start with when we slow down we are disapating energy through our brakes so we will be wasting more energy when we brake with a larger wheel as it has more energy stored with in it.

There are many detailed considerations when considering the performance differences between 26" and 700c wheels. Note that the analysis presented below considers the wheels as the only variable and hence fails to take into account that the wheels are only part of the system which comprises "a bicycle".

The ratio in rim diameter between the two is roughly 700/559 = 1.25. Imagine two nearly identical bicycles where only the wheels are different--and also the gearing to make the gear-inches come out the same on each one. So the hubs are the same, same number and gauge of spokes (shorter on the 26"), same cross sectional area on the rims and tires, same tire pressure.

The main considerations in comparing these two hypothetical bikes are due to differences in mass, geometry, dynamics, frictional and aerodynamic losses, and also the intangible factors of the road surface, terrain, and the size and weight of the rider. So at the smallest level of detail these are really quite different bikes. But what are the significant differences?

The 700c wheel has a 25% smaller "attack angle" of the wheel (neglecting the tire) so a 25% higher bump will feel the same compared to the 26" wheel. On certain rough surfaces the 700c wheel could also have less rolling friction. The hypothetical 700c bike will weight more (because the rims and tires of our hypothetical 700c bike have larger diameter and the spokes are longer). To put this in perspective, let's say the wheels are 1/4 of the total weight of the bike so that the overall weight has gone up by roughly 1+0.25*.25 = 1.125 (say 10%). Thus there is more mass to transfer linear momentum to and more rotating mass at a greater radius to transfer and store angular momentum (and kinetic energy) in. The 700c bike will accelerate more slowly on the flats for the same input torque (power input) but will keep rolling longer under its own momentum and angular momentum. In principle the frontal area presented to the wind for the 700c wheel and spokes will be slightly greater so there will be a slightly increased aerodynamic loss due to this but overall this will be a negligible effect given that this difference is small compared to the total frontal area.

Theoretically, the hypothetical 26" wheeled bike will ride slightly rougher and possibly have slightly higher rolling friction. It will accelerate slightly faster but slow down faster under frictional and aerodynamic drag. The 26" bike will have a slower terminal velocity on long, steep downhills. Because there are more spokes per linear rim diameter length, and because there is less lateral leverage on the shorter spokes, the 26" wheel will be stronger. Less total mass will mean less energy expended when climbing.

Up to speed on the flats there should be little difference between 700c and 26". The hypothetical 700c will be smoother in both the vertical plane (due to smaller attack angle of the wheels) and in the direction of travel (due to greater inertia). The 26" will have slightly larger frictional losses in the bearings since its angular velocity is higher but slightly lower aerodynamic losses 'cause they're smaller...the relative effects of these are negligible in practice. It is possible that the 700c could end up with a slight edge due to its theoretically lower rolling friction.

It is climbing on long hills where greater mass requires greater energy input (which is never fully recovered on the downhill) for the same elevation gain that the lighter bike might be thought to be decisively more efficient. The hypothetical 700c will take about 10% more energy. However, even this depends on intangible details (like the size and weight of the rider, length of the climb, the next downhill and the presence of a following hill) since under certain circumstances (like just the right size and spacing of rolling hills) the heavier bike would preserve fractionally more kinetic energy with which to attack the next hill. Conceivably, this could compensate for the inefficiency of the previous climb if it were short enough.

To summarize this analysis of hypothetical bikes: The hypothetical 26" bike is both lighter and stronger (than the hypothetical 700c bike) which are both good things that the hypothetical 700c can only respond to with a slightly smoother ride and the hope of slightly reduced rolling friction.

In practice it is rare to find such hypothetically identical bikes. In N. America, usually, 26" wheels and tires are thicker and thus heavier. These thicker tires now become smoother than before. The frames are usually made correspondingly heavier to take advantage of the stronger wheels. Thus, the practical situation is often just the opposite of that presented in the above hypothetical analysis. In my situation, I have a Surly LHT with 26" wheels that weighs about 32lbs and a Specialized Roubaix with 700c wheels weighing about 19lb. Guess which one I'd rather climb the next hill with. Guess which one I take touring.

Lightweight 26" tourers are pretty rare but are a speciality of Thorn in the UK.
They have an interesting discussion (http://www.thorncycles.co.uk/why26inchwheels.html)of the relative merits of 26MTB vs 700c wheel size for non-competative touring use.

Sounds to me like there is no obvious and distinct advantage to one over the other, more so preference. So assuming I pull the trigger on the 26" LHT as my next frame...

Any suggestions on "roadie" worthy 26" wheels and tires?
(I'll be using this bike as a part-time tourer and a part-time long-distance roadie (no bags))

Thanks!

Sounds to me like there is no obvious and distinct advantage to one over the other, more so preference. So assuming I pull the trigger on the 26" LHT as my next frame...

Any suggestions on "roadie" worthy 26" wheels and tires?
(I'll be using this bike as a part-time tourer and a part-time long-distance roadie (no bags))

Thanks!

Now you went from touring to randonneuring. For your stated purpose(s) you might be happier with 700c wheels, While there are slick narrow road tires available for 26" there are not many. It is easier to find quality touring tires for a 700c wheel than quality 26" narrow slicks for fast tours.

"Hey I am also working on my 69 but I am going to use the bike for offroad (mainly) tourism. I am going to use special designed by titerra (titerra.com) ti front fork (29'') and ti frame (26''). I do not believe 69 is better for cross country race but for offroad cycling especially with rigid fork is a really good idea."

vigur, great to know it makes sense to someone else. I should mention that mine is not really a 69er in the MTB sense since that implies a front wheel with greater diameter still, given the 2" + tire. Mine is really a 26" x 1.3/8", combined with a 700C x 37, or someting in that order. I will try to get decent enough clearance to run largish tires, though probably not to the extent of a true 29er fork.

"as a wheel increases in diameter, it rolls more easily over obstacles; this is a good argument for 700c wheels…" as per Thorn brochure.

Bontrager had an interesting take on that relative to 29er vs 26er. He said it isn't true in most cases. it takes energy to go up over a bump, and you get the energy back in either case going back down. The only difference is if the tire starts to loose contact with the road, then you fall down and you loose forward energy. It's therefore a more limited set of cases where tire fit to the obstacle is an issue and you go airborn. These fit issues are probably not limited to one size only, but it seems logical the larger wheel is less likely to get air than the smaller, most of the time. Just the same it is a narrow slot where the 26 isn't ahead, or where both don't jump off the bump. On other cases you are lugging around the extra weight of the larger wheel.

That's not a quote but a recolection of what he said.

This does not address the greater potential comfort of the larger wheel, which can itself affect fatigue.

"as a wheel increases in diameter, it rolls more easily over obstacles; this is a good argument for 700c wheels…" as per Thorn brochure.

Bontrager had an interesting take on that relative to 29er vs 26er. He said it isn't true in most cases. it takes energy to go up over a bump, and you get the energy back in either case going back down. The only difference is if the tire starts to loose contact with the road, then you fall down and you loose forward energy. It's therefore a more limited set of cases where tire fit to the obstacle is an issue and you go airborn. These fit issues are probably not limited to one size only, but it seems logical the larger wheel is less likely to get air than the smaller, most of the time. Just the same it is a narrow slot where the 26 isn't ahead, or where both don't jump off the bump. On other cases you are lugging around the extra weight of the larger wheel.

That's not a quote but a recolection of what he said.

This does not address the greater potential comfort of the larger wheel, which can itself affect fatigue.

This sounds like a smokescreen to me. Larger wheels can mount taller obstacles more easily - that is a fact which anyone can confirm by trying to roll a wheel of X radius over an square obstacle that is X+something and then trying it again with a wheel of 2X radius. The bigger the wheel, the more lever arm the CG of the vehicle has to roll over the obstacle. Simple physics. That's why dirt motorcycles tend to have 21" front wheels and street motorcycles have 17" front wheels - to allow the dirt motorcycle to more easily surmount obstacles such as rocks and roots.

Tangent: The abiltiy of larger wheels to more easily roll over objects is one of the primary drivers for the 29'er movement. The convention to use 26" wheels for mountain bikes is mainly because when mountain bikes were first developed, most of the wider tires were in the smaller 26" size. Personally, I think 26" mountain bikes wheels are going to be virtually gone in new bikes within 5-10 years - the 29'er movement has got real technical legs and this is the main reason why.

Lots of other factors to consider, but if your only objective is to roll more easily over objects in your path, bigger is better.

- Mark

For my purposes, I'm not concerned about obstacles.

No offense to 29er advocates for the purpose of smoother rolling, but just shift your weight back immediately before the obstacle and it'll lift your front wheel. It eventually becomes second nature. And I suck at mtb'ing :)

Any suggestions on "roadie" worthy 26" wheels and tires?
(I'll be using this bike as a part-time tourer and a part-time long-distance roadie (no bags))


Essentially, what you'll end up buying or building will be a mountain wheelset for your LHT. The LHT uses 135mm dropouts so you'll end up with a mountain hub, and as far as rims, 26" mountain bike rims. Mounting skinny slicks on them will make the bike not only lighter, but more road worthy.
I have 3 sets of mountain bike wheels which I use between my LHT and my mountain bike. The wheelsets have knobbies, touring, and slicks mounted on them. Also the wheelset with the skinnies have a smaller small cog and a tighter cluster.

"This sounds like a smokescreen to me. Larger wheels can mount taller obstacles more easily - that is a fact which anyone can confirm by trying to roll a wheel of X radius over an square obstacle that is X+something and then trying it again with a wheel of 2X radius. The bigger the wheel, the more lever arm the CG of the vehicle has to roll over the obstacle. Simple physics. That's why dirt motorcycles tend to have 21" front wheels and street motorcycles have 17" front wheels - to allow the dirt motorcycle to more easily surmount obstacles such as rocks and roots."

Take it up with Keith Bontrager. The podcast he made this statement on can probably be searched, it was some guy who has a bike "radio" show. Maybe this is it, I am on 56K so check it out:

http://crookedcogpodcast.com/2006/10/13/episode-6-interbike-wrapup-and-keith-bontrager-interview/

If you examine your own statements, though, it stands out that they say nothing about the energy that returns on the way back down a bump. It is not disputed, as far as I know, that the longer lever arm means a more gradual rise to the top of a bump, and smoothness is important, both for comfort and not taking air. But as you come off the bump on the way down the other side you recover your energy, minus waste. Your example of a square object pretty much guarantees air in the real world, at speed. But what about some more typical rises, like a smoothish speed bump where one would roll down the far side. Not to mention many energy sucking "bumps" that one hardly feels at all. You are simply selecting those objects that fall only into the category I mentioned above as being advantageous to larger wheels. The other two categories are smaller bumps, and ones that send either wheel into the air.

I'm not expert on the 29er, but it does not seem to be taking the world by storm. It seems to be taking the hip oddity part of the world by storm. It's great business for custom frame builders for a reason.

"No offense to 29er advocates for the purpose of smoother rolling, but just shift your weight back immediately before the obstacle and it'll lift your front wheel. It eventually becomes second nature. And I suck at mtb'ing"

What is under discussion affects the blacktop rider just as much. We all know how much worse roads with cracks, waves, or ruts ride, and these are micro versions of the same thing we face off road, and they suck big energy. Then there are those who tour offroad. The maneuver you suggest is fine, now and again. On severe surfaces one depends on the bike to smooth things out.

Essentially, what you'll end up buying or building will be a mountain wheelset for your LHT. The LHT uses 135mm dropouts so you'll end up with a mountain hub, and as far as rims, 26" mountain bike rims. Mounting skinny slicks on them will make the bike not only lighter, but more road worthy.
I have 3 sets of mountain bike wheels which I use between my LHT and my mountain bike. The wheelsets have knobbies, touring, and slicks mounted on them. Also the wheelset with the skinnies have a smaller small cog and a tighter cluster.

Thanks for the info! And your set up is exactly what I'd like to do. (sorry to all if I didn't communicate my needs and goals very well :o )

If you'll indulge me...

The knobby set up you have, do you use your LHT as a kind of rigid XC MTB? Do you take it on easier single-track?

How thin are your slicks? On a brief search, I found...

Schwalbe Stelvio 26" High Pressure Tire (http://www.westernbikeworks.com/productdetail.asp?p=SCVIO) -- 26x1.1 Folding Bead (28-559, 115 Max. PSI, 250 grams)

Schwalbe Marathon has a great reputation in the Commuter forum, so I'm assuming these are worthy tires as well. Thing is, can a mtb wheel actually hold a 1.1" (28mm) tire?

Thanks for everyone's help!

You have to carefully sellect your rims. One of the great rims of all time, no loger made, was the Mavic MA2. I have a version Bontrager made in 36 hole for MTBs, and like all MA2s it is 20.5 mm wide. He was marketing them for 2"+ knobbies. So the smaller rims will carry a wide range of tires. If you start out with very wide rims then you have trouble mounting narrow tires, and they weigh too dang much, and part of that weight is there because the wider rim is weaker, were it attempted on the same sections as narrow rims, so you get to eat the weight twice. The CR18s, are 22.5, the Rhynolites are 27.5 which is one reason to avoid them. Mavic makes a range of rims from 20.3 to 24.6 that are appropriate for touring.

I do something similar to what Roadfix does, except I don't change the cluster, start with the narrow rims for everything, and just change the tires. Generally you can just grab a 26" tire and break it off the rim by hand. Though I often use a quickstick. I have a compressor so that at home where I make these changes I don't have to hand pump the tires.

I run Schwalbe Marathon slicks. Not the perfect tire for offroad, or punctures, though my current set has been 2000 loaded miles without a puncture. I find that when fully inflated they really run fast at 38 mm. I'd go down to 32 mm, but I am not convinced much narrower tires are faster for the way I ride. They would be faster for something, doubtless.

Just a plug for schwalbe big apples, fantastic tires w/ my 54cm LHT... the skinny ones, the 2.0s! If I thought I could jam the 2.35s under my fenders I would try.

Hmm, is it just my creaking system, or did they trim Keith's comments from that podcast?

(I'll be using this bike as a part-time tourer and a part-time long-distance roadie (no bags))


Just to throw something into the mix, have you thought of the Cross Check or any other sport touring bikes? The LHT is nice when loaded but I would personally prefer to use something else for no load or light load long distance rides.

Just to throw something into the mix, have you thought of the Cross Check or any other sport touring bikes? The LHT is nice when loaded but I would personally prefer to use something else for no load or light load long distance rides.
Why don't you like the LHT for no load riding? I keep hearing people say that, but the only response I've seen so far is that it's "sluggish". That doesn't really mean much to me.

One advantage I've read is that the longer chain stay makes it more stable and that in turn makes it track better through downhill turns.

(I've already got a single-speed that I use in-town, just FYI)

Thanks again!

Why don't you like the LHT for no load riding? I keep hearing people say that, but the only response I've seen so far is that it's "sluggish". That doesn't really mean much to me.

For no load around town riding it's fine. It's just that I have other road bikes which I prefer to use for long distance day rides, even with a light load, therefore the LHT feels sluggish when compared with my other bikes. I often use my LHT to commute, lightly loaded, and I love it.....but I'm only riding less than 10 miles one way.
I guess several factors come into play, as some may interpret a very stable ride as sluggish, and also the weight, as the LHT is noticeably heavier.

I'm sure you are right about what you are feeling, on the other hand: A heavy frame is really not a problem. The difference is about the same as adding a second water bottle, not a big deal. Now if every component on the LHT is bought from the bargain basement "lourd" basket it probably is a pig, but that is hardly an LHT problem.

I think I read a post somewhere by Jobst Brandt of the Bicycle Wheel fame where he said every training ride he goes on he hits 55 mph. I gather he goes high up into the mountains and there are wild decents. One thing he is known for, apparently is having the longest chain stays on his custom bike that he can find, they would be a good deal longer than the LHT, possibly 2 or more inches. Not really sure why, but he is a fast rider, a tourist who does 3000 miles regularly, credit card style, in the Alps, yet he has really long stays (or so I am told). I think a lot of people think the correct geometry for the rest of us is a peleton inspired twitchy drafting machine, when really any riding the non-racer does should probably be done on a geometry more like an LHT or even much longer in the stays than that.

I think a lot of people think the correct geometry for the rest of us is a peleton inspired twitchy drafting machine...
I have a huge problem with that. I go to buy supplies at my LBS and hear the idiots chanting the marketing mantra.

Why is almost every mass produced road bike designed for racers instead of people? Is it the Lance-effect?

I have a huge problem with that. I go to buy supplies at my LBS and hear the idiots chanting the marketing mantra.

Why is almost every mass produced road bike designed for racers instead of people? Is it the Lance-effect?
I don't think it has much to do with any particular athlete, especially since there are quite a few bikes made for non-racers. Walk into a shop, tell them you haven't cycled in 10 years, and 9 times out of 10 they'll steer you towards a hybrid.

In the road bike category, there's plenty of non-racing bikes; "Roubaix" or "plush" or "performance" or "sport" road bikes are fairly popular, and aren't made for racing. The thing is, the relaxed all-day-comfort type road bikes (like a full-on touring bike) just aren't fast and/or don't feel fast. And, well... unless you're touring, fast is fun. ;)